Summary: This paper proposes a new algorithm to control an adaptive duplexer for multiband software radio. It uses a wideband low isolation device combined with a two-tap/two-loop adjustable canceller to eliminate the need for multiple switched high isolation duplexers. The taps are adjusted to provide isolation peaks in the transmit and receive bands. The algorithm is based on the superposition of squared errors and achieved 66 dB isolation of the transmit signal and a 37 dB cancellation of the transmitter noise in the receiver band.